The field of the present invention is apparatus and methods for providing access to a patient""s central venous system and/or heart, and producing heat exchange with a body fluid flowing through the patient""s central venous system.
Cardiovascular guiding catheters are typically used in patients undergoing heart surgery to provide a path through a patient""s vasculature through which other medical apparatus, such as other catheters or stent devices, may be advanced. Guiding catheters may also supply a conduit through which a contrast dye may be injected for diagnostic procedures, or through which other, smaller therapeutic catheters may be placed and maneuvered toward the patient""s heart. Conventional cardiovascular guiding catheters are typically about 5 to 10 French in size and have a flexible single-lumen elongated body extending 80 to 110 centimeters. They typically may be introduced through the left or right coronary ostium, the subclavian or jugular veins, or through the femoral vein of the patient, serving to provide the caretaker with easy and convenient access to the patient""s central blood supply via the central venous system. In this manner general access to the central blood supply is gained, enabling, for example, delivery of drugs, constrast dyes, fluids, along with the gathering of patient blood for blood gas analysis and the like.
One specific application for a guiding catheter is in balloon angioplasty procedures. Balloon angioplasty is a medical procedure used to widen narrowings in the coronary artery without surgery. The major challenge to angioplasty is clinical restenosis, or the re-narrowing of the blood vessel following the angioplasty procedure. Coronary stenting is a technique which mechanically props open the artery through implementation of a small, latticed stainless steel tube at the site of the narrowing. The stainless steel tubexe2x80x94the stentxe2x80x94is pre-mounted on a coronary angioplasty balloon catheter. As the balloon catheter is inflated during angioplasty, the stent expands and is compressed against the artery walls. When the balloon is deflated, the expanded stent remains implanted in the artery.
An introducer sheath may be inserted into a patient""s vein to facilitate insertion of the guiding catheter. This sheath provides a direct and smooth pathway for the catheter to enter the artery. A coronary guiding catheter is inserted into the introducer sheath and may be advanced to the part of the aorta where the coronary arteries branch off to the heart. A hemostatic valve, which controls the flow of blood through the artery, is attached to the end of the coronary guiding catheter to allow for the insertion of coronary catheters. Note that a coronary guiding catheter is a conduit for the coronary guide wire and the coronary catheters to access the coronary artery. Coronary catheters rely on the support provided by the coronary guiding catheter.
A coronary guide wire is loaded into the coronary guiding catheter through the use of a guide wire introducer, and advanced to the cardiac vessel just past the narrowing. Coronary guide wires are used to support the coronary catheters as they are advanced across the artery narrowing. A torque device is placed on the end of the coronary guide wire and is used to steer the coronary guide wire to the artery until its tip is beyond the narrowing.
A coronary stent catheter is inserted at the distal end of the coronary guide wire and is advanced across the narrowing over the coronary guide wire through the guiding catheter.
After the plaque has been compressed and the artery has been opened sufficiently, the deflated coronary stent catheter may be withdrawn through the coronary guiding catheter, which itself is then removed.
In addition to using a guiding catheter to provide access to a patient""s central venous system and/or heart, it may be desirable to reduce the patient""s body temperature below normal body temperature so that the patient experiences hypothermia. Many advantages of hypothermia are known. By way of example, it has been found desirable to lower body temperature to reduce the metabolism of the body. This has been particularly desirable in surgical applications where the reduced metabolism has made it possible to more easily accommodate lengthy operative procedures. In cases of stroke and several other pathological conditions, hypothermia also reduces the permeability of the blood/brain barrier. It inhibits release of damaging neurotransmitters and also inhibits calcium-mediated effects. Hypothermia also inhibits brain edema and lowers intracranial pressure. In other cases, it may be desireable to cool a patient experiencing a fever so that the patient""s body temperature returns to normal. Evidence suggests that cooling the body core is protective for the myocardium and the brain. Particularly, during accute myocardial infarction (AMI) and cardiac arrest (CA), the myocardium is deprived of adequate oxygen for extended periods of time and the brain is vulnerable to blood embolisms resulting from the impaired heart. These conditions can potentially be improved when the body is maintained at subnormal temperatures (32xc2x0 C.-36xc2x0 C.) during treatment. In treatment of myocardial infarction, angioplasty and stenting operations may also be included.
In yet other situations, it may be desirable to raise the patient""s body temperature. Control of a patient""s temperature may be problematic during hospital stays and particularly during active interventions such as surgery. The patient""s body temperature may drift too low during surgery, potentially being deterimental to the patient""s health. In such cases, body temperature may be artificially maintained at a normothermic temperature (approximately 98.6xc2x0 F.). With regard to heart surgery, it may be particularly desireable to cool a patient before and/or during heart surgery and re-warm the patient post-operatively.
Conventional therapies used to manage patient temperature include acetaminophen (Tylenol), cooling blankets, heating blankets such as warm water blankets, forced warm or cool air, heat lamps, endovascular catheters, ice packs, ice baths, cold or warm infusions, and cold saline rectal or gastric ravages. With some of the conventional therapies, the warming or cooling rates are restricted by the body""s ability to resist surface cooling or heating with vasodilation and sweating. The conventional approaches to cooling a patient also may require additional steps, may require excessive time and may not provide for precise control of patient temperature over long periods of time. Further, some of these devices cover a significant portion of a patient""s body, inhibiting access to the patient.
Other techniques for controlling patient temperature employ intravascular heat exchange catheters that may be inserted into the patient""s circulatory system. A relatively cool or warm fluid may be circulated through such catheters in a closed loop and exchange heat with blood flowing in the circulatory system, and may improve the patient""s medical outcome.
Carrying out both the guiding function of a cardiovascular guiding catheter and the heat transfer function of a heat exchange catheter conventionally requires the use of two separate devices. Compared with using a single catheter, using both a heat exchange catheter and a cardiovascular guiding catheter would increase the complexity of the procedure, require addional steps to be carried out, and may require an additional incision.
In order to minimize the number of incisions and cardiovascular guiding catheter insertions into the patient""s body and cool or heat the patient relatively quickly and in a controlled fashion, a cardiovascular guiding catheter may be configured to include a heat exchange capability.
By supplementing the known functions of a cardiovascular guiding catheter with the function of cooling or warming the patient""s blood, a cardiovascular guiding catheter may take advantage of existing access to the venous system using a single, relatively small incision, reducing the risk of additional complications. One access is through the iliac arteries. Additional access may be through the subclavian, jugular or femoral veins to the central blood supply, via the central venous system, and is therefore particularly expedient, permitting efficient cooling or warming of a patient. The term central venous system generally relates to the portion of the venous system which returns blood to the right side of the heart, including the inferior and superior vena cava.
It would be advantageous to provide a single cardiovascular guiding catheter that provides access to the patient""s heart and bloodstream, facilitates guiding of other medical apparatus in the bloodstream, and provides intravascular cooling and heating, thereby overcoming one or more problems associated with the related art.
The present invention is directed to a heat exchange cardiovascular guiding catheter and methods for its use. A heat exchange element or elements is combined with a guide lumen and guide duct to provide efficient temperature control of a patient, to provide convenient access to the patient""s heart and/or central venous system, and to provide a pathway through which medical apparatus may be advanced in the patient""s bloodstream, all with a single catheter. Using a single catheter allows both the heat transfer function and the guiding function to be carried out simultaneously and reduces the complexity of providing the functions with two separate conventional devices.
In a first separate aspect of the invention, a heat exchange catheter comprises a guiding lumen and duct that facilitate insertion of medical apparatus in a patient""s central venous system, and a heat exchange element that exchanges heat with the patient""s blood so that a single cardiovascular guiding catheter carries out both the guiding function of a standard cardiovascular guiding catheter and the heat transfer function of a heat exchange catheter.
In a second separate aspect of the invention, a heat exchange cardiovascular guiding catheter comprises a generally tubular elongate body defining an inflow lumen, an outflow lumen, and at least one guide lumen. The inflow and outflow lumens supply heat exchange fluid to and from one or more heat exchange elements disposed about a distal, implantable portion of the catheter, while the guide lumen provides a pathway and access to the heart and/or central blood supply of the patient.
In a sixth separate aspect of the invention, a heat exchange cardiovascular guiding catheter is provided with multiple balloons (preferably three or four balloons) that are spaced along the elongated body to provide controlled and balanced heat transfer, with a gap between balloons to provide the catheter with flexibility.
In an eighth separate aspect of the present invention, it is contemplated that combinations of the foregoing separate aspects may be incorporated into a single embodiment.
Therefore, it is an object of the present invention to provide an improved heat exchange cardiovascular guiding catheter and a method for its use. Other and further objects and advantages will appear hereafter.